The above-described cooling system with a storage tank for the cooling liquid and a separate expansion tank for the expansion of the liquid during warming-up is used for example on heavier trucks and buses where very high functional safety requirements are imposed.
Where the available height is restricted, it has been usual to use separate tanks which are mounted by brackets and connected together by means of tubes and tube clamps. This implies that a relatively large number of components have to be stored and assembled during the production of a vehicle. Since it is desirable to reduce the number of assembly components, combined storage tanks and expansion tanks forming a common container tank are now becoming available. This rationalization is most effective if the container tank is made from two injection-moulded plastic halves which are welded together to form a finished unit with all necessary functions integrated within the two halves.
Such a container tank is shown in DE OS 35 33 095, whereby the storage tank and the expansion tank are connected via a centrally located overflow channel. A disadvantage with this arrangement, i.e. that leakage can arise between the two chambers, has been solved by the provision of a double walled partition wall between the two chambers, whereby infiltration is indicated by leakage of liquid through overflow holes in the double walled cavity.